This invention relates to a hydrophilic porous membrane, a method of manufacturing the same and a liquid filter using the same.
In the general solution administration filter for medical treatment, a porous membrane is used as a filter for removing foreign particles and bacteria in solution administration. Such a porous membrane should be superior in mechanical strength and separation performance.
Heretofore, to obtain a porous membrane having excellent mechanical strength and separation performance a hydrophobic porous membrane is rendered to be hydrophilic. This may be done, for instance, by a method, in which the membrane surface is given a hydrophilic group by using an aqueous solution containing such alkali as NAOH or KOH, as disclosed in Japanese Patent Disclosure 58-93734, or by a method, in which a hydrophobic porous membrane is immersed in alcohol, then treated with an aqueous solution of water-soluble polymer and then dried, followed by rendering the water-soluble polymer remaining on the surface insoluble with heat rays or like means, as disclosed in Japanese Patent Disclosure 54-17978.
However, the above methods of rendering a hydrophobic porous membrane hydrophilic have the following problems. In the former method, in which the membrane surface is given a hydrophilic group in a treatment with an aqueous solution of alkali, the mechanical strength of the membrane is liable to be reduced. In the latter method, in which the membrane is treated with an aqueous solution of a water-soluble polymer and then dried, followed by rendering the residual polymer insoluble with heat rays or the like, a long time is required from alcohol osmosis until substitution with the aqueous solution of polymer. Further, at the time of treatment of rendering the residual polymer insoluble, the pore diameter of micropores of the membrane is liable to be changed to deteriorate the separation performace.